law enforcement officials familiar with the case say they appear to have consisted of an explosive and shrapnel backed inside a pressure cooker, probably triggered by some kind of timer. if that is the case, we have seen this before. one of the three devices used in the 2010 attack in times square incorporated a pressure cooker containing approximately 120 fire crackers. a soldier, nazir abdul, convicted last year of plotting an attack at ft. hood, texas, was using a bomb-making recipe from an al qaeda-linked online magazine that used a pressure cooker. in july of 2006, more than 130 died in a series of attacks on the mumbai transit system with pressure cooker explosives placed on the trains. the department of homeland security has warned of the potential terrorist use of pressure cookers saying "as a common cooking utensil, the pressure cooker is often overlooked when searching vehicles, residences, or merchandise crossing the u.s. borders." now, of course, there's still much more that authorities want to know about this particular case. and for the very latest on the investigation, w